Self-selection

Amino acids essential for young rats (98) and fishes (99) have been reviewed. Rats preferably eat a diet with sufficient amounts of essential amino acids rather than one that is deficient (100). Each essential amino acid, consumed in self-selection, has been reviewed (101). A protein diet with an excess of essential amino acids has been described as a poor protein diet from investigations that showed remarkable growth inhibition and occurrence of fatty fiver disease in rats (102). This is called amino acid imbalance (103). 

The authors chose pyruvic acid as their model compound this C3 molecule plays a central role in the metabolism of living cells. It was recently synthesized for the first time under hydrothermal conditions (Cody et al., 2000). Hazen and Deamer carried out their experiments at pressures and temperatures similar to those in hydrothermal systems (but not chosen to simulate such systems). The non-enzymatic reactions, which took place in relatively concentrated aqueous solutions, were intended to identify the subsequent self-selection and self-organisation potential of prebiotic molecular species. A considerable series of complex organic molecules was tentatively identified, such as methoxy- or methyl-substituted methyl benzoates or 2, 3, 4-trimethyl-2-cyclopenten-l-one, to name only a few. In particular, polymerisation products of pyruvic acid, and products of consecutive reactions such as decarboxylation and cycloaddition, were observed the expected tar fraction was not found, but water-soluble components were found as well as a chloroform-soluble fraction. The latter showed similarities to chloroform-soluble compounds from the Murchison carbonaceous chondrite (Hazen and Deamer, 2007). 

Hatchell PC, Collins AC. The influence of genotype and sex on behavioural sensitivity to nicotine in mice. Psychopharmacology 1980 71(1) 45—49. Robinson SF, Marks MJ, Collins AC. Inbred mouse strains vary in oral self-selection of nicotine. Psychopharmacology 1996 124(4) 332—339. 

For one week prior to and following the 45-day controlled diet period of HS-II and HS-III, each individual collected duplicate portions of all food and liquids consumed. These self-selected diets were brought to the laboratory and daily composites were prepared for analysis. 

Table IV. Mean Calcium Utilization from Self-Selected and High Fiber, Low Cholestrol, Low Fat Controlled Diets by Human Adults...

Self-selected, 40% or less calories from fat < 10 g fiber > 500 g cholesterol 1462a 498a 762a 52. la 47.9a 202a... 

These results apparently support those in the previous study however, because dietary fiber was higher in the low fat diet than in the high fat diet, it is impossible to separate the effects of fat, fiber and possibly cholesterol. The alterations used in the low fat, controlled diet were essentially those recommended in the U.S. Dietary Goals/Guidelines while the moderately high fat, self-selected diets resembled usual American dietary intake patterns. 

Another question involving interpretation is whether these patterns are merely a reflection of different "food habits" of the individuals concerned, since all the individuals were on self-selected diets. The answer to this question appears to be that, although dietary differ-... 

Before discussing the problem of self-selection of foods and its relationship to individuality in nutrition, we should emphasize at this point that individual differences in nutritional needs may have many basic causes. 

We cannot take the space here to review the rather extensive literature dealing with self-selection of food this subject has been discussed elsewhere.87,88,89 Instead, we will summarize present-day knowledge of the subject, particularly as it relates to the problem of individual nutritional needs. 

Self-selection of foods has not been studied from the standpoint of individual differences. We know by observation that some individuals have a "sweet tooth," that "Jack Sprat can eat no fat," etc., but we have no idea except by inference how these characteristics fit in with the metabolic peculiarities of the individuals concerned. 

Limitations of Self-Selection A New Method of Detecting Nutritional Deficiencies... 

E. M. Scott and others, series of articles on self-selection of diet in J. Nutrition beginning 1946. 

See also research, medical biochemical individuality and, 206-207 metabolism, 203 variations, exceptions and, 202 vision, 202-203 vitamin research and, 204-205 scopolamine, 228 scurvy, 167-168 self-esteem, genetics and, 16 self-selection of foods, 180 Selye, Hans, 230 senile dementia, 34-35, 227, 230 sensory physiology and psychology, 205 serotonin, 236 serum amylase, 80-81 serum lipase, 81 serum phenol sulfatase, 81 sex behavior, 100, 104-105 psychiatry and, 231 sex differences... 

Figure 1.3 Self-selection in coordination complex formation.

For self-selection experiments and selection in the presence of an organic guest, this is generally a simple criterion to satisfy. However, biomolecules dramatically narrow the available conditions the reaction must ideally occur at room temperature and in buffered aqueous solution. Both of these conditions can be (at least in principle) attained by physically separating the scrambling reaction from the biomolecule against which the library is selected. 

Figure 1.9 Pd pi-allyl-mediated self-selection (Sanders).

Alkyne metathesis, a mechanistic cousin of alkene metathesis, has thus far found only limited exploration. In 2004, Zhang and Moore reported that precipitation-driven alkyne metathesis reactions could efficiently produce arylene ethynylene macrocycles [50]. This was explored further in a 2005 report, verifying that the products obtained were indeed the result of thermodynamic self-selection [51]. 

Figure 1.13 Self-selection of molecular boxes via olefin metathesis.

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